Is this an anchor or is it a cross? The answer, it is both. Not only is it both, it is a truly ancient Christian symbol.
So why did Christians think to combine the two? The anchor has long been seen as a symbol of hope and faith. Going to sea was a terribly dangerous thing to do and many never returned. It was a leap of Faith just to venture out. There have been many times in history when Christians have been persecuted, this particular symbol became their secret declaration of faith.
One of the first examples of the creation of this symbol can be found around 100 A.D. The emperor Trajan banished the fourth pope, St.
Clement, to the Crimea. When the pope converted the people there, Trajan
ordered that Clement be tied to an iron anchor and drowned. Tradition
holds that the sea then receded three miles to reveal Clement's body
buried by angels in a marble mausoleum. Whether all the details of this
tale are exactly true or not, but the story of Clement's martyrdom clearly inspired the
persecuted Church.
During the Roman Empire Christians were terribly persecuted. Even fed to lions as entertainment.
The Roman Emperor Constantine (306-337) actually converted to Christianity. The cross replaced the anchor as a source of encouragement to believers in troubled waters. It was no longer needed by Christians to secretly identify themselves, as now the Empire formally embraced the religion.
Other scholars, though, think the anchor slipped from use because the "symbol" was actually a word play in Greek—ankura resembling en kurio, or "in the Lord"—which disappeared as Christians chose Latin over Greek as their primary language.
The anchor did reappear in
the 1600s, when it experienced a two-century renaissance, particularly
as a symbol engraved on tombs.
Today if you search, you can still find this ancient cross used on tombs. Now you know what it means.